Mogollon Airpark Airport
Aircraft Accident/Incident Report

Overgaard, Arizona 85933
Saturday, August 10, 2013 7:00 MST

The pilot reported that, during takeoff, the airplane became airborne but that it did not accelerate as he expected and that the engine was not producing full power. The pilot adjusted the fuel mixture to full rich and switched fuel tanks with no change in performance. Subsequently, the pilot initiated a forced landing to an open area beyond the departure end of the runway. During the landing, the airplane struck a ravine and then came to rest upright. During an engine test run, the engine ran normally until reaching about 2,000 rpm, at which point, it began to run roughly and black smoke began expelling from the exhaust. Examination of the exhaust system found that the baffles within the muffler assembly were partially separated and restricted the airflow ducts within the exhaust. The restricted airflow would result in a loss of engine power at higher engine rpm settings. No additional mechanical anomalies were observed with the recovered engine that would have precluded normal operation. The airplane manufacturer’s service manual contained a warning stating, “a very thorough inspection of the entire exhaust system, including the exhaust heater shroud assembly, muffler and muffler baffles, stacks, and all exhaust connections and welds must be accomplished at each 100-hour inspection.” Further, the service manual contained a note stating, “all PA-28 airplanes be fitted with a new muffler at or near the 1,000-hour period of which the muffler has been used.” The most recent 100-hour/annual inspection was completed at an engine time since overhaul of 1,257 hours. At the time of the accident, the airplane had accumulated about 8 hours of operation since the annual inspection. The annual inspection logbook entry for the engine noted that the exhaust system was inspected; however, a review of the engine and airframe logbook records revealed no entries noting that the muffler or exhaust system was replaced.

The partial loss of engine power during takeoff due to the separation of the exhaust baffling, which resulted in a partial blockage of airflow. Contributing to the accident was inadequate maintenance of the exhaust system.